1. Field of the Invention
The present invention relates to a pointing device to be used as an operating device of an electronic apparatus, such as a mobile phone, a PDA, or a game controller, and to a key sheet to be used in the pointing device, in particular, a magnetism detection type pointing device which detects a change in magnetic flux density through lateral movement operation of a key top to determine a lateral position of the key top and which also functions as a key capable of performing confirmation input through key top depressing operation, and to a key sheet for the pointing device.
2. Description of the Related Art
Operating devices for electronic apparatuses and the input systems for them are being diversified. In this context, there is known a magnetism detection type pointing device which detects with a magnetic sensor a change in magnetic flux density due to “lateral movement” of a magnet through, for example, tilting of a key top, and which utilizes this change as a lateral position input signal. Above all, a pointing device which also functions as a key capable of confirmation input through key top depressing operation is used as an input key of a mobile phone, etc., and is disclosed, for example, in JP 2004-62447 A. As shown in FIG. 10, in such a pointing device, a magnet is embedded and retained in a key top to be operated.
In a magnetism detection type pointing device (1) as shown in FIG. 10, a magnet (2) is inside a key top (3), so the distance between the magnet (2) and magnetic sensors (4) is rather large. Thus, to attain a sufficient sensitivity property, it is necessary for the magnet (2) to be large or for the magnetic force to be strong. An attempt to meet this demand results in an increase in the thickness of the key top (3), an increase in the weight of the pointing device (1), etc. Further, when a magnet with strong magnetic force is used, there is a fear of the magnetic force being leaked to the exterior to adversely affect peripheral devices, a magnetic card, etc.
Further, the key top (3) is used to effect directional input (lateral position input) through lateral movement operation and confirmation input through depression of a contact belleville spring (Po) on a board (P) by depressing the key top in a direction substantially perpendicular to the lateral movement direction to thereby bring a board contact (Pi) into conduction, so that it is necessary for the key top (3) to be capable of moving vertically and horizontally. However, a large movable range for the key top (3) and a high degree of freedom in movement thereof can lead to an increase in the looseness of the key top (3) at the time of operation, making it rather difficult to effect accurate depressing operation. When the depressing operation is not properly effected on the key top (3), erroneous input or erroneous operation results.